Life has been around for quite some time, billions of years in fact. Estimates say that life began on Earth not so long after the planet itself formed. Now, there's evidence that life was thriving, or at least existing, on Earth as far back as 3.49 billion years ago.These are the oldest traces of life on Earth, though it's likely further study will push the date back even further.
There are no fossils that far back, but scientists have been able to find signs that life existed one billion years after the Earth took shape.
Analyzing some of the oldest rocks on Earth, scientists found signs that life was around, specifically, they found marks left in the rocks which indicate a microbial mat was living on them all that time ago.
These patterns are called Microbially Induced Sedimentary Structures (MISS). Microbial mats formed on what was originally a coastal plain, on sand.
They also found that the ratio of the Carbon 13 isotope to Carbon 12 were consistent with organic material, indicating that life was present on the surface of the rocks all that time ago.
The different types of bacteria and other organisms there left their mark on the sand which eventually turned into stone, a process that's still happening today in some places.
Specifically, the thick microbial mats trap sand particles inside but protect them from corrosion. In time, this sand turns to rock of a different composition to those formed via the same process but without the organisms present.
Scientists were analyzing rocks found in the Pilbara region of Australia, where some of the oldest in the world can still be found. They traced these rocks to some 3.49 billion years ago. Previously, the oldest known signs of life were dated to 3.4 billion years ago and were found in the same region.
There are older rocks on Earth, but these are some of the best preserved, making them more likely to reveal the tiny structures scientists look for.